The present invention relates to a method for transferring film bags which are supplied by a supply means in a plurality of parallel rows to a conveying means which further transports the film bags in a continuous row, and to an apparatus for performing the method.
Nowadays, film bags which are used as packing means are mostly treated automatically, for instance filled, closed and further processed. Such film bags consist e.g. of two side films that are sealed to one another at three edges and between the fourth edge of which a bottom film is sealed in that when said bottom film is unfolded room is created in the film bag for the filled product.
In such an automated processing line, several film bags are often treated side by side at the same time. For instance, a number of film bags are simultaneously opened in a filling means, further transported by a transportation device, filled at the same time, further transported again and then closed at the same time.
However, at other points of the processing line, the film bags must be supplied individually to a processing station. A typical example is e.g. the application of drinking straws to beverage film bags.
This creates the problem that the film bags must be transferred by a transportation means which supplies a number of film bags in parallel, to another transportation means from which the film bags are discharged in a single row for further processing. This results in a discontinuous operation because a supplied number, corresponding to the row number supplied in parallel, must always be handed over simultaneously while the conveying means is at a standstill. Moreover, on account of the speeds nowadays used in such processing systems, strong acceleration and deceleration forces are created during transfer, which especially in the case of film bags may easily cause damage.
Said object is achieved by a method comprising the features of claim 1 and by an apparatus comprising the features of claim 6. Advantageous developments are the subject matter of the respective subclaims.
According to the method of the invention a respective number of film bags which are simultaneously supplied to a transfer station are received all at once by a transfer device, preaccelerated by said device in the direction of movement of the conveying means, discharged to the conveying means and then transported away by the latter substantially in a direction perpendicular to the direction of supply. The method according to the invention permits a continuous operation. While a number of film bags are being transported by the transfer device to the conveying means and handed over to the latter, a further number of film bags are supplied by the supply means to the transfer station. On the other hand, the conveying means continues its travel, transporting away already transferred film bags for further processing while the transfer device takes over a new number of film bags from the supply means and transports the bags to the conveying means. With a corresponding setting of the relative speed between the supply means and the conveying means a continuous operation is thereby ensured. Moreover, the preacceleration of the received film bags in the conveying direction has the effect that the acceleration forces are reduced upon discharge to the conveying means. Thus, damage upon discharge to the conveying means is prevented. Small acceleration forces during discharge also enhance the accuracy of the positioning operation for the bags on the conveying means
The method according to the invention is particularly efficient when the speeds of the conveying means and of the transfer device are matched such that the conveying means transports away a number of film bags which have simultaneously been handed over, within the same period in which the transfer device has received a further identical number of film bags and transported and preaccelerated the same for discharge to the conveying means. It is thereby ensured that the capacity of the conveying means is exploited in an optimum way because no irregular distances on the discharge device can be created between the individual film bags. Moreover, this facilitates the further processing in automated processing stations.
Advantageously, in the method of the invention the relative speed between the conveying means and the film bags at the moment of discharge to the conveying means may be zero or almost zero. Thus, acceleration forces acting on the film bags are entirely avoided during discharge, whereby the risk of damage to the film bags is further reduced and the accuracy of the bag positioning operation is increased.
The film bags are simply transported away by the conveying means in a slightly inclined position. Such an inclined position permits an easy discharge operation because the film bags are held on the discharge device on account of their inclined position.
The film bags can directly be deposited on the conveying means by the transfer device However, it is easier when the film bags are lifted from the supply means, transported via the conveying means and released at said place. The demands made on a precise discharging operation are thereby reduced.
For performing the method of the invention, the apparatus according to the invention comprises a supply means which supplies film bags in parallel rows, a conveying means which transports away the film bags in a continuous row substantially in a direction perpendicular to the supply direction, and a transfer device which takes over from the supply means a respective number of film bags corresponding to the number of supplied rows, preaccelerates said bags in the direction of movement of the conveying means and discharges the same to the conveying means.
The transfer device can perform the individual movements e.g. in the manner of a robot controlled by a microprocessor. A particularly simple configuration is however a transfer device which comprises a carrier, a transverse bar parallel thereto with carrier means for the film bags and at least one lever arm which interconnects the transverse bar and the carrier, the connections being designed such that the angle enclosed by the lever arm with the carrier or transverse bar is variable. Such an arrangement permits a preacceleration of the received film bags in an easy way by varying the angle.
Such a construction is particularly stable if at least two lever arms are provided so that the carrier, the lever arms and the transverse bar form a parallelogram of a variable angle.
The angle can be varied in various ways. One simple possibility consists in pivoting a lever arm with the help of a motor. Said motor can be controlled such that upon discharge of the film bags the transverse bar and the conveying means have a relative speed of zero or almost zero. Acceleration forces can thus not act on the film bags during the discharge operation, which reduces the risk of damage. Advantageously, the movement of the transverse bar in the area of the conveying means is so high that it is slightly higher than a film bag positioned on the conveying means. It is thereby avoided that the movement of the transverse bar might impede the transportation of the film bags. Moreover, it is thereby easily possible to release the film bags to the conveying means, which represents a simple possibility of discharge.
To this end the transverse bar can perform a lifting movement during the transfer operation. To this end a linkage guide is just provided that effects the lifting movement during change in the angle between the at least one lever arm and the carrier. Such a linkage guide represents a possible configuration that is simple, mechanical and inexpensive. The lift can also be carried out pneumatically or by a motor.
The carrier means may comprise clamps on the transverse bar that are capable of gripping the film bags at the upper end thereof. The supply means may be an endless belt on which a number of film bags are conveyed in parallel.
Receiving cases in which the film bags are supplied may be arranged on the endless belt. The supply means may consist of chains extending in parallel and including receiving cases mounted thereon, in which the film bags are supplied.
The discharge means may e.g. comprise a transportation belt. Advantageously, holding means are provided on such a transportation belt, the film bags being transported in said means. Such holding means ensure a safe transportation. Such a safe transportation can be realized in a particularly easy manner when the holding means are designed such that the film bags are transported in a slightly inclined position.